I.  ATOMIC  WEIGHT  OF  TUNGSTEN 
II.  AMMONIUM  TUNGSTATES. 


THESIS 

Presented  to  the  Faculty  of  the  Department  of  Philosophy 
of  the 

University  of  Pennsylvania 
In  Partial  Fulfillment  of  the  Requirements 
for  the 

Degree  of  Doctor  of  Philosophy 


BY 

THOMAS  MAYNARD  TAYLOR 

OBERLIN,  OHIO 


PHILADELPHIA 
Priestley  Printing  Company 


ACKNOWLEDGMENT. 

This  study  was  prosecuted  under  the  direction  of  Pro- 
fessor Edgar  F.  Smith.  It  is  only  with  appreciation  of  the 
privilege  of  working  under  his  direction,  that  I offer  my 
thanks,  to  him  whose  love  for  chemistry  is  an  inspiration 
and  whose  kindness  that  of  a father. 


DEC  2 9 ’15 


INTRODUCTION. 


- f 

(A 


h 


The  object  in  mind  when  the  present  investigation  was 
undertaken,  was  not  primarily  the  establishment  of  the 
atomic  weight  of  tungsten.  It  was  rather  to  ascertain  by 
working  up  unusually  large  quantities  of  “starting-out 
material’’  to  discover  whether  there  were  not  present 
minute  quantities  of  other  elements,  which  accompanied 
the  tungsten  through  its  many  compounds,  and  escaped 
recognition  in  the  numerous  efforts  put  forth  to  get  a pure 
product.  These  experiments  have  brought  to  light  the 
facts  which  are  detailed  in  Part  I.  They  constitute  a defi- 
nite contribution  to  our  knowledge  of  disturbing  factors  in 
the  determination  of  this  particular  constant. 

The  ammonium  tungstates  as  described  in  Part  II.,  show 
interesting  relationships.  The  suggestions  as  to  constitu- 
tion are  instructive,  but  can  only  be  adopted  after  we 
possess,  definite  experimental  evidence  as  to  the  molecular 
weights  of  these  compounds.  The  existence  of  the  colloidal 
ammonium  salt  is  rather  in  the  nature  of  a surprise,  although 
its  frequent  reproduction  and  the  concordant  analyses  prove 
its  individuality,  and  that  it  is  not  a chance  product.  The 
manner  in  which  water  is  substituted  for  ammonia  and  visa 
versa  recalls  the  deportment  of  salts  of  copper  in  the  same 
direction,  and  gives  additional  confirmatory  evidence  of 
this  behavior  of  hydrated  and  ammoniated  bodies. 


V 


$ 

o 


(3) 


Digitized  by  the  Internet  Archive 
in  2016 


/ 


https://archive.org/details/atomicweightoftuOOtayl 


I.  ATOMIC  WEIGHT  OF  TUNGSTEN. 


The  wide  variability  in  the  atomic  weight  determinations 
of  tungsten,  suggest  that  there  is  some  impurity,  or  pos- 
sibly some  closely  associated  element,  which  clings  tena- 
ciously to  tungsten  and  its  derivatives.  With  a view  of 
searching  for  this  disturbing  factor,  and  of  finding  a more 
accurate  method  than  those  hitherto  used,  the  following 
study  was  undertaken. 

The  material  used  had  been  extracted  from  11.34  kilo- 
grams of  Wolframite  from  Conn.,  and  had  undergone  the 
following  treatment: 

1st.  Tungsten  trioxide  was  separated  from  Wolframite 
by  aqua  regia,  and  washed  with  acidulated  water. 

2nd.  This  oxide  was  dissolved  in  distilled  ammonia. 

3rd.  The  ammonium  tungstate  was  crystallized,  and  the 
first  fraction  collected,  which  being  deposited  from  a large 
bulk  of  water  was  unusually  white. 

4th.  This  fraction  was  redissolved  in  water  and  ammo- 
nia, and  again  crystallized,  and  the  first  fraction  preserved. 

5th.  This  perfectly  white  salt  was  ignited  in  porcelain 
crucibles  to  bright  “canary  yellow’  * tungsten  trioxide. 
Oftentimes  on  long  ignition,  a faint  blush  of  red  was  noticed 
on  the  surface  of  the  yellow  oxide. 

The  method  of  reduction  and  oxidation  has  been  the  one 
most  generally  used,  and  to  test  the  method  the  following 
experiments  were  made:  A portion  of  the  trioxide  was 

placed  in  a porcelain  boat,  and  reduced  in  hydrogen,  using 
a thin  walled  porcelain  combustion  tube,  glazed  inside  and 
out.  The  apparatus  for  generating  and  purifying  the 


(5) 


6 


hydrogen  was  the  same  as  that  used  by  b)Hardin,  and 
worked  satisfactorily.  The  porcelain  tube  was  heated 
directly  with  free  flames,  to  the  highest  heat  obtainable  in 
a combustion  furnace. 

The  weighings  in  these  experiments  were  made  on  a 
Troemner  short  arm  balance,  sensitive  to  the  fortieth  of  a 
milligram,  supplied  with  calibrated  weights.  No  reduc- 
tions to  a vacuum  standard  were  made. 


Reduction  No*  f* 


Time 

Weight  of  W03 

Weight  of  W Atomic  Weight 

Hours 

grams 

grams 

of  Tungsten 

(1) 

3 

1.74898 

1.3861 1 

183.35 

(2) 

6 

1.74898 

1-38589 

183.21 

(3) 

9 

1.74898 

1-38587 

183.20 

The  material  was  not  removed  from  the  boat,  during 
these  reductions.  As  the  time  of  heating  progressed  the 
atomic  weight  became  lower,  and  after  nine  hours  it  did. 
not  become  constant.  The  experiment  was  repeated  with 
another  sample: 


Reduction  No*  2. 


Time 

Weight  of  W03 

Weight  of 

W Atomic  Weight 

Hours 

grams 

grams 

of  Tungsten 

(1) 

4 

1.20096 

0.95214 

183.67 

(2) 

7 

1.20096 

0.95203 

183.57 

(3) 

1 1 

1.20096 

0.95182 

183.38 

(4) 

14 

1.20096 

0.95174 

183.30 

(5) 

18 

1.20096 

0.95141 

183.00 

(6) 

22 

1.20096 

o.95i34 

182.93 

Constant  weight  was  not  obtained  after  heating  for 
twenty-two  hours. 


b)«7.  Am.  Ch.  Soc.,  19,657.  (1897). 


7 


Reduction  No.  3. 


Time 

Weight  of  W03 

Weight  of  W Atomic  Weight 

Hours 

grams 

grams 

of  Tungsten 

4 

2.77973 

2.20447 

183-94 

8 

2 77973 

2.20423 

183.84 

The  metal  from  the  twenty-two  hour  reduction  was  oxi- 
dized in  a porcelain  crucible,  in  an  atmosphere  of  oxygen 
for  one-half  hour. 

Oxidation  Experiment  No.  \ ♦ 

Time  Weight  of  W Weight  of  W03  Atomic  Weight 
Hours  grams  grams  of  Tungsten 

°-5  0.93574  1.17882  184.77 

It  is  observed  that  the  same  metal , which  on  reduction 
gave  values  from  183.67  to  182.93,  on  oxidation  gives 
184.77.  Another  portion  of  tungsten  trioxide  was  ignited 
over  a single  Bunsen  burner  in  oxygen  for  three  hours,  and 
a loss  noted. 

Oxidation  Experiment  No.  2. 

Time  Weight  of  WOs  Weight  of  W03  Loss 
Hours  grams  grams  grams 

3 2.99239  2.99175  0.00064 

Another  sample  of  tungsten  trioxide  (which  had  been 
prepared  from  the  metal  ignited  in  air),  was  ignited  for  one 
hour  in  oxygen,  and  a gain  noticed.  After  further  ignition 
in  oxygen  for  one  hour,  a loss  was  observed. 

Oxidation  Experiment  No.  3. 

Weight  of  W03  Weight  of  W03  Weight  of  W03 

grams  after  one  hour  after  two  hours 

1-57355  1-57449  1-57285 


8 


After  the  first  hour  it  gained  0.00094  grams;  after  the 
next  hour,  it  lost  0.00070  grams.  The  explanation  is 
probably,  that  the  tungsten  trioxide  used  had  not  quite 
reached  its  maximum  oxidation.  When  ignited  in  oxygen 
it  was  fully  oxidized,  and  further  ignition  produced  a loss. 
The  current  of  oxygen  used  was  extremely  slow  (bubble  by 
bubble),  so  that  mechanical  sweeping  out  of  the  material 
could  hardly  have  occurred. 

The  porcelain  tube  employed  in  these  reductions  was 
new.  After  use,  it  was  swabbed  with  filter  paper,  which 
now  showed  dark  spots.  The  porcelain  boats  were  white, 
but  after  the  reductions  they  were  dark  all  over  the  outside, 
and  even  on  the  bottom.  In  some  cases  the  porcelain  boats 
were  partly  surrounded  with  platinum  foil,  and  a deposit 
occurred  on  the  porcelain  in  such  a manner,  that  the  posi- 
tion protected  by  the  platinum  foil  was  clearly  marked  on 
the  outside  of  the  boat,  by  being  lighter  in  color.  The 
platinum  also  was  stained  with  a deposit.  On  oxidation 
the  darkened  sides  of  the  boat  became  nearly  white,  so  that 
the  dark  material  was  undoubtedly  tungsten. 

From  a consideration  of  these  results  it  appears,  that  with 
the  material  used,  and  by  varying  the  conditions  of  reduc- 
tion or  oxidation,  almost  any  figure  could  be  obtained  for 
the  atomic  weight  of  tungsten.  How  different  determina- 
tions may  be  reduced  or  oxidized  to  a constant  and  com- 
parable weight,  is  difficult  to  understand.  It  probably  can 
only  be  done  by  making  the  conditions  precisely  alike  in 
every  determination.  A requirement  which  at  times  may 
be  misleading. 

A few  more  determinations  by  this  method  were  made, 
on  the  tungsten  trioxide  contained  in  colloidal  ammonium 
tungstate.  In  this  case  the  reductions  were  continued  for 
three  hours,  and  the  oxidations  for  one  hour  in  oxygen; 
and  all  determinations  were  made  as  nearly  alike  as  pos- 
sible, so  that  the  results  might  be  comparable. 


9 


Reduction  Series* 


Weight 

Weight 

Atomic 

Material 

of  W03 

of  W 

Weight  of 

grams 

grams 

Tungsten 

(1) 

Dialyzed  (13  days) 

2.35730 

1.86939 

183.91 

(2) 

Undialyzed 

2 39381 

1.89763 

I83-57 

(3) 

First  fraction 

2.13506 

1.68995 

182.24 

Oxidation  Series. 


Weight 

Weight 

Atomic 

Material 

of  W 

of  W03 

Weight  of 

grams 

grams 

Tungsten 

(1) 

Dialyzed  (13  days)  0.72938 

0.91954 

184. 11 

(2) 

Undialyzed 

0.62988 

0.79346 

184.82 

(3) 

First  fraction 

0.48514 

o.6i 166 

184.05 

These  results  show,  that  the  tungsten  trioxide  from  the 
dialyzed  salt,  gives  a higher  atomic  weight  than  the 
material  passing  through  the  parchment  paper.  The  varia- 
tion in  the  difference  between  the  reduction  and  the  oxida- 
tion values,  for  the  three  different  portions,  is  marked. 
This  difference  for  the  dialyzed  material,  is  0.20;  for  the 
undialyzed.  1.25;  and  for  the  first  fraction  (that  portion 
passing  through  in  twelve  hours),  1.8 1.  These  results 
therefore  indicate  that  dialysis  is  removing  some  crystalloid 
from  the  material,  and  that  this  substance  is  responsible  for 
the  difference  between  the  reduction  and  oxidation  values. 

The  tungsten  trioxide  resulting  from  these  determinations 
was  dissolved  by  boiling  in  a solution  of  pure  sodium  car- 
bonate, when  a white  flocculent  residue  remained.  The 
dialyzed  material  contained  the  same  residue,  but  in  smaller 
amount.  When  dissolved  in  potassium  hydroxide  the  resi- 
due was  not  so  evident.  On  standing  a few  hours  in  sodium 
carbonate,  this  residue  turned  reddish  brown.  On  treat- 
ment with  hot  concentrated  hydrochloric  acid,  it  (having 
been  previously  washed)  broke  down  into  tungstic  acid, 


IO 


and  the  filtrate  contained  the  chlorides  of  iron  and  man- 
ganese. To  confirm  the  presence  of  these  impurities  in  the 
metal  from  the  reductions,  it  was  boiled  with  pure  hydro- 
chloric acid,  and  iron  detected  in  the  liquid.  Moreover, 
this  iron  could  not  be  entirely  removed  by  boiling  acid. 
To  see  if  some  of  the  original  ammonium  tungstate  would 
reveal  the  presence  of  these  impurities,  it  was  dissolved  in 
water,  feebly  acidulated  with  hydrochloric  acid,  and  am- 
monium sulphocyanate  added.  No  coloration  was  pro- 
duced. Another  portion  of  the  solution,  was  boiled  wfith 
hydrochloric  acid,  the  tungstic  acid  precipitated,  and  now 
the  filtrate  easily  showed  the  presence  of  iron. 

This  residue  appears  to  be  a tungstate  of  iron  and  man- 
ganese, which  probably  existed  in  the  ammonium  salt,  as 
an  ammonium-iron-manganese  tungstate,  (dj^aurent  states, 
that  the  mother  liquor  from  which  ammonium  tungstate 
has  been  crystallized  contains  such  a salt.  He  ascribed  to 
it  the  formula:  <(l) 2)[i2  (NH4)20,  6 MnO,  2 Fe20„  3 H20, 
45  WO.,  81  H20]. 

(3) Borch  analyzed  this  salt  with  the  following  results: 
W03  84.4%,  (Fe203+Mn203)  4.6%,  NH3  4.0% , H20  7%. 
Laurent  states  that  this  complex  salt  is  soluble  in  water  and 
ammonia,  and  is  peculiar,  in  that  ordiuary  reagents  do  not 
show  the  presence  of  iron,  manganese,  or  tungstic  acid. 
Further,  that  the  salt  is  only  broken  down,  by  prolonged 
boiling  in  acids  or  alkalies,  and  then  the  ingredients  can  be 
readily  detected. 

(4)  Schneider  recognized  the  presence  of  this  salt  in  ammo- 
nium tungstate,  and  stated  that  after  five  or  six  recrystal- 
lizations, it  could  not  be  removed-  Also  that  it  could  not 
be  removed  by  the  ammonium  sulphide  treatment,  for  slight 

(l) J.prakt . Ch.}  42,126.  (1847). 

WComptes  rendus. , 31,693-  (1850). 

(3 )J,  prakt.  Ch.,  5 4,254.  (1851). 

MJ.  prakt.  (7A.  ,50,152.  (1850). 


II 


amounts  of  the  sulphides  of  iron  and  manganese,  are  sol- 
uble in  the  tungsten  sulpho-salt.  (^Berzelius  stated  that 
the  sulphides  of  tungsten,  iron,  and  manganese,  form  a 
compound  which  is  partly  soluble  in  water.  ^Taggart  and 
Smith  have  shown  that  manganese  and  tungstic  acid  can 
not  be  separated  by  yellow  ammonium  sulphide,  nor  by 
aqueous  potassium  carbonate;  and  suggest  the  necessity  of 
fusion  with  an  alkaline  carbonate. 

Schneider,  to  remove  this  complex  salt,  purified  his 
material  in  the  following  way:  Tungstic  acid  obtained  from 
the  sulpho-salt  of  tungsten,  was  boiled  in  aqua  regiay  and 
washed  in  acidulated  water  till  free  from  iron.  This  was 
dissolved  in  dilute  ammonia,  and  the  solution  precipitated 
by  boiling  hydrochloric  acid,  the  resulting  tungstic  acid 
boiled  in  aqua  regia  and  again  washed.  This  oxide  was 
again  dissolved  in  ammonia  and  again  precipitated.  After 
reprecipitating  three  times  in  this  manner,  a tungsten  tri- 
oxide was  obtained  free  from  iron.  However,  on  dis- 
solving the  oxide  in  potassium  hydroxide,  a slight  brown 
residue  remained  which  had  escaped  all  earlier  tests.  The 
small  amount  of  this  as  he  assumes,  was  not  enough  to 
affect  the  result  of  his  work. 

A portion  of  the  material  used  in  the  previous  experiments 
in  this  paper, was  treated  with  this  reprecipitation  method.  It 
was  dissolved  in  ammonium  hydroxide,  precipitated  by  boil- 
ing in  aqua  regia,  the  resulting  oxide  washed.  This  moist 
precipitate  (without  ignition)  was  again  dissolved  in  ammonia 
and  reprecipitated.  In  this  manner  the  material  was  repre- 
cipitated four  times.  A portion  of  it  was  then  dried,  ignited, 
and  dissolved  in  boiling  sodium  carbonate.  The  residue 
very  materially  diminished  was  still  there,  and  particularly 
noticeable  after  standing  a few  hours.  Another  portion  of 


WPogg.  Ann.,  8,279.  (1826). 

(2)J.  Am.  Ph.  Soc.,  $8,1053.  (1896). 


12 


this  substance  apparently  dissolved  completely  in  boiling 
potassium  hydroxide,  but  on  standing  twenty-four  hours  a 
slight  deposit  was  observed.  In  no  case  was  this  deposit  as 
large  as  that  in  the  comparison  tube  of  sodium  carbonate; 
which  would  indicate  that  the  residue  is  more  soluble  in 
potassium  hydroxide,  than  in  sodium  carbonate.  Schneider 
admits  that  his  purest  material,  showed  a trace  of  residue 
when  dissolved  in  potassium  hydroxide.  Had  he  applied 
the  sodium  carbonate  test,  this  residue  would  probably  have 
appeared  larger.  In  the  recent  repetition  of  his  Wwork,  he 
used  material  purified  in  precisely  the  same  manner,  (in 
fact  some  of  the  original  material)  with  the  exception  of 
the  treatment  for  the  elimination  of  molybdic  acid. 

(2)Borch  recognized  this  complex  salt,  and  tried  to  remove 
it  by  fusion  with  potassium  carbonate.  However,  this 
treatment  introduces  fixed  alkali,  which  is  difficult  to 
remove. 

Later  investigators  seem  not  to  have  appreciated  the  diffi- 
culty of  removing  this  complex  salt;  for  it  crystallizes  in 
part  with  the  ammonium  tungstate,  and  can  scarcely  be 
entirely  removed  by  recrystallization.  Ignition  of  the 
ammonium  salt,  and  resolution  in  ammonium  hydroxide 
will  not  eliminate  it.  Nqj  will  ammonium  sulphide  remove 
it.  In  fact  it  seems  likely  that  it  has  never  been  wholly 
extracted,  from  any  previous  material. 

The  purification  by  (^Pennington  and  Smith,  would  not 
remove  it,  for  though  closely  following  the  method  outlined 
by  Schneider,  and  adding  to  it  the  complete  elimination  of 
molybdenum;  they  omitted  the  final  repeated  precipitations 
with  acid.  The  metal  used  by  them  had  the  specific  gravity 
18.64,  which  appears  low.  Had  the  metal  been  alloyed 
with  platinum,  its  specific  gravity  would  have  been  higher, 


WJ.  prakt.  Oh .,  161,288.  (1896). 

(2)J.  prakt.  Gh..  54,254.  (1851). 

(z)Proc.  Am.  Philos , Soc.,  33,332.  (1894). 


13 


but  tliis  metal  gave  no  test  for  platinum.  ^Moissan  pre- 
pared metallic  tungsten  in  the  electric  furnace;  which  was 
soft,  would  not  scratch  glass,  and  could  be  easily  filed  and 
welded  like  iron;  produced  no  effect  on  the  magnetic 
needle,  and  examined  spectroscopically,  showed  the  pres- 
ence of  no  foreign  ingredients,  other  than  faint  lines  for 
calcium.  It  fused  with  more  difficulty  than  chromium  or 
molybdenum,  and  gave  the  following  analysis: 


Tungsten 

Carbon 

Gangue 

Per  cent. 

Per  cent. 

Per  cent. 

(1) 

99.76 

00.00 

00.18 

(2) 

99.82 

00.00 

00.09 

(3) 

99.87 

00.00 

00.00 

The  specific  gravity  of  this  metal  was  18.7,  and  the  pres- 
ence of  gangue  would  have  lowered  the  specific  gravity,  so 
that  the  true  value  is  probably  higher. 

The  process  of  purification  employed  by  Hardin  for 
tungsten,  would  not  remove  the  complex  salt. 

A review  of  the  original  material  used  by  previous  work- 
ers, shows  that  Schneider,  Marchand,  Borch,  Pennington 
and  Smith,  Desi,  Shinn,  and  probably  nearly  all  the  others, 
used  Wolframite  as  the  “starting-out  material’ In  some 
cases  the  source  of  material  has  not  been  stated.  Waddel 
started  with  Scheelite,  but  abandoned  it  for  commercial 
metal  of  unstated  origin. 

This  complex  salt,  obviously  can  not  come  from  Scheelite, 
which  is  essentially  a calcium  tungstate.  Determinations 
with  Scheelite  material  have  been  made  by  (2)Hardin,  and 
(3)Thomas  and  Hardin.  The  results  for  the  purpose  of 
comparison  are  again  presented: 


b)  Comptes.  rendus .,  123,13-1 6.  (1896). 

(2) J.  Am.  Ch.  Soc. , 19,657.  (1897). 

(3 ) J.Am.  Ch.  Soc .,  21,373-  (1899). 


H 


Scheelite  from  New  Zealand.  Hardin, 


Reduction  Series 
Atomic  Weight 


Oxidation  Series 
Atomic  Weight 


183.83 
18380 
183.67 
183.56 
183.72 
183.71 
183.80 
183  87 


183.83 

18375 

184-13 

183.90 

183.82 

184.20 


Mean  183.74 


183.94 


The  difference  between  the  mean  of  the  two  series  is  0.19. 
The  quantities  of  material  used,  varied  from  two  to  four  and 
a half  grams.  To  quote  Hardin  concerning  these  results: 
“Considering  the  number  of  experiments,  this  is  the  most 
concordant  series  of  results  ever  obtained  by  reducing  the 
trioxide  of  tungsten  and  weighing  the  resulting  metal.” 

Scheelite  from  Bohemia.  Thomas  and  Hardin. 


The  difference  between  the  mean  of  these  two  short 
series  is  0.36.  Some  Scheelite  contains  iron,  and  this  may 
account  for  the  greater  difference  from  the  preceding 
series. 

Hardin’s  determinations  with  Wolframite  material,  show 
generally  a difference  of  nearly  a whole  unit.  Concerning 
this  discrepancy  he  says:  ‘ ‘Almost  every  series  of  results 

on  the  atomic  mass  of  tungsten  obtained  by  the  reduction 


Reduction  Series 
Atomic  Weight 

183.89 

183.63 


Oxidation  Series 
Atomic  Weight 

184.17 

184.08 


Mean  183.76 


[84.12 


15 


of  the  trioxide  in  a current  of  hydrogen,  and  by  the  reoxi- 
dation of  the  resulting  metal  shows  a variation  between  the 
maximum  and  minimum  results  of  from  one  to  two  units, 
and  in  exceptional  cases  the  deviation  is  much  greater.” 
‘ ‘It  seems  that  the  results  from  oxidations  are  invariably 
higher  than  those  obtained  by  reduction.” 

To  Hardin’s  results  obtained  from  the  metal  which  had 
been  prepared  from  the  second  reduction  of  the  oxide,  this 
difference  for  some  reason  is  not  so  marked.  His  results 
would  indicate  (since  the  second  reduction  value  is  higher 
than  the  first),  that  the  oxide  prepared  in  this  way,  had 
not  reached  its  maximum  oxidation.  Undoubtedly  through 
repeated  reductions  and  oxidations,  the  material  will  take 
up  considerable  silica,  which  may  retard  complete  oxidation. 

This  discrepancy  between  the  reduction  and  oxidation 
series,  must  be  explained  before  any  great  weight  can  be 
attached  to  the  recorded  values  of  tungsten.  To  under- 
stand the  effect  of  possible  impurity,  the  following  table  is 
given:  A molecular  mixture  of  tungsten  and  the  impurity, 

is  treated  as  though  it  was  all  tungsten,  and  the  resulting 
atomic  weight  calculated. 


Molecular  Mixture 

W+W 
W+Mo 
W+2Fe 
W+3MnO 
Toss  of  Material 


Reduction  Series 
Atomic  Weight 

184. 

140. 

148. 

298. 

Low 


Oxidation  Series 
Atomic  Weight 

184. 

140. 

148. 

298. 

High 


A consideration  of  these  numbers,  shows  that:  Molyb- 
denum and  iron  would  produce  a low  value;  manganese  a 
high  value;  volatility  a low  value  on  reduction,  and  a high 
value  on  oxidation.  The  error  introduced  by  manganese 
is  more  than  three  times  as  costly  as  that  introduced  by 
iron,  and  more  than  two  and  a half  times  that  introduced  by 


i6 


molbydenum.  These  ratios  would  apply,  regardless  of  the 
proportion  of  the  mixture. 

The  discrepancy  between  the  reduction  and  oxidation 
series,  can  not  be  explained  by  assuming  the  presence  of 
iron,  manganese,  or  molybdenum.  But  loss  of  material 
would  cause  such  a difference.  Tungsten  is  a heavy  metal 
and  such  a perceptible  loss  as  that  noted  in  the  experiments 
in  this  paper,  would  certainly  cause  a discrepancy  between 
the  two  values. 

There  is  little  difference  between  the  reduction  and  oxida- 
tion series  which  Hardin  obtained  from  Scheelite,  and  little 
difference  between  the  two  series  given  by  Schneider.  If 
loss  by  volatility,  be  advanced  to  explain  this  discrepancy, 
then  in  these  series  just  mentioned,  little  volatilization  could 
have  occurred.  If  loss  through  mechanical  carrying  away 
of  the  material  by  water  be  advanced,  then  in  these  series 
the  water  could  not  have  carried  away  much  material. 
Hardin  does  not  state  that  volatility  was  noticed  in  his 
Scheelite  series,  and  Schneider  states  that  no  appreciable 
volatility  occurred  with  his  material.  Other  reasons  must 
therefore  be  sought  to  explain  this  loss  of  material. 

The  specific  gravity  and  fusibility  of  tungsten  is  such, 
that  it  seems  improbable  that  it  would  volatilize  in  the 
temperature  attained  in  a combustion  furnace.  It  is  known 
that  alloys  melt  at  temperatures  far  below  the  melting  point 
of  the  most  fusible  ingredient,  and  the  volatility  would  be 
affected  in  like  manner.  Moissan  showed  that  the  purified 
tungsten  had  a noticeably  higher  melting  point  than  the 
impure,  and  that  this  melting  point  was  greater  than  that 
of  chromium  or  molybdenum.  It  seems  quite  likely  that 
iron  and  molybdenum,  even  in  traces,  alloying  with  the 
tungsten  would  materially  increase  the  volatility. 

From  these  considerations  it  is  believed,  that  the  presence 
of  manganese  and  iron,  will  account  for  the  high  oxidation 
values,  for  their  presence  would  affect  the  result  in  a two 


i7 


fold  manner:  Manganese  through  its  inherent  molecular 

chenges  [Mn304^fZZl!^3  MnO] , and  iron  through  its  sec- 
ondary action  on  the  volatility.  Further,  that  the  presence 
of  iron,  molybdenum,  manganese,  and  volatility,  will 
explain  the  numerous  discrepancies  noted  in  the  published 
work  on  this  subject.  Again,  since  iron  and  molybdenum 
decrease  the  value,  and  manganese  and  volatility  increase 
the  value,  and  iron  and  molybdenum  influence  the  volatility: 
It  is  quite  possible  that  such  a mixture  of  these  factors 
might  occur,  that  the  errors  would  be  compensated.  And 
such  material,  not  only  would  give  concordant  reduction 
and  oxidation  values,  but  might  even  give  values  close  to 
the  true  constant. 

Viewed  in  this  way  there  still  remains  the  necessity  for 
determinations  with  material  from  which  every  trace  of 
molybdenum,  iron,  and  manganese,  together  with  other 
possible  impurities,  has  been  removed.  And  in  all  proba- 
bility such  material  will  yield  values  close  to  those  obtained 
by  Schneider,  and  Hardin  with  his  Scheelite  material. 

The  reduction  and  oxidation  method  is  so  simple  and 
direct,  that  it  will  be  abandoned  only  as  a last  resort. 
Possibly  the  reduction  and  oxidation  could  take  place 
through  the  walls  of  a porous  porcelain  capsule,  and  any 
loss  be  thus  prevented;  the  porous  walls  acting  as  a perfect 
filter  for  the  aqueous  vapor,  and  at  the  temperature  used 
hydrogen  or  oxygen  would  find  no  difficulty  in  entering. 
Schneider  has  shown  that  the  hot  aqueous  vapor  produced 
in  the  reduction,  attacks  the  porcelain  boat  and  produces  a 
slight  deposit  of  silica  on  a platinum  foil  placed  over  the 
boat. 

Schneider’s  material  contained  a trace  of  residue,  which 
with  the  sodium  carbonate  test  would  doubtless  have 
appeared  larger.  (^Smith  and  Oberholtzer  have  shown 


''V 


WJ.  Am.  Ch.  Soc .,  f5,i8.  (1893). 


i8 


that  the  previous  methods  usually  employed  for  removing 
molybdic  acid  have  been  inadequate.  In  view  of  these 
considerations  it  seemed  desirable  to  experiment  with  new 
methods;  new  methods  for  preparing  pure  material,  and 
new  methods  for  determining  the  atomic  weight.  In  any 
case,  the  application  of  a new  ratio  will  be  of  value. 

A benzylamine  tungstate  has  been  prepared  in  this  labor- 
atory, which  may  throw  some  light  on  the  subject.  These 
organic  salts  may  afford  a means  of  separation  and  puri- 
fication. A solvent  may  be  found,  suitable  for  molecular 
weight  determinations.  Pending  the  investigation  of  this 
side  of  the  question,  the  following  new  method  was  tried. 

The  method  of  determining  atomic  weights  from  the  loss 
of  carbon  dioxide  has  been  applied  to  a number  of  the 
elements.  Its  application  to  tungsten,  and  the  special 
modification  of  the  method  necessary  for  accurate  deter- 
minations has  not  been  before  recorded.  (^Svanberg  an(l 
Struve,  fused  molybdenum  trioxide  with  potassium  car- 
bonate and  determined  the  loss  in  weight.  Their  value  is 
nearly  six  units  too  low  and  the  method  must  be  considered 
inaccurate.  This  method  was  tried  with  tungsten  trioxide 
and  gave  values  ranging  from  160.  to  180.  The  disad- 
vantages of  the  method  are  that:  The  union  takes  place 

with  considerable  spattering;  the  temperature  of  fusion  is 
so  high  that  loss  by  volatility  is  probable;  the  alkaline  car- 
bonates when  held  in  fusion  slowly  lose  traces  of  carbon 
dioxide;  and  the  resulting  fusion  is  extremely  hydroscopic. 

These  difficulties  may  be  obviated  by  combining  the 
oxide  and  sodium  carbonate  in  aqueous  solution,  and  then 
expelling  the  water.  Operated  in  this  manner  the  method 
possesses  promising  value;  and  has  numerous  advantages, 
among  which  may  be  mentioned  that:  Carbon  dioxide  has 

a molecular  weight  of  forty-four,  giving  a value  for  com- 


WJ.praJct.  Ch.,  44,301.  (1848). 


19 


parison  nearly  as  great  as  in  the  simple  reduction  and  oxi- 
dation method;  the  union  of  sodium  carbonate  and  tungsten 
trioxide  in  aqueous  solution  takes  place  at  a low  temper- 
ature, and  the  highest  temperature  used  in  the  desiccator  is 
a safe  distance  below  the  melting  point  of  sodium  carbonate, 
so  that  there  is  little  chance  for  volatilization  either  of 
sodium  carbonate  or  tungsten  trioxide,  and  in  the  device 
used  there  is  no  chance  for  loss  by  spattering;  large  quan- 
tities of  material  may  be  combined  with  as  much  ease  as 
small;  the  method  itself  would  serve  for  a test  of  the  purity 
of  the  material;  the  presence  of  chlorides,  sulphates,  sodium 
silicate,  and  potassium  carbonate,  would  not  affect  the 
result.  The  presence  of  alkaline  hydroxides  would;  and  to 
prevent  the  possibility  of  this,  “pure’  ’ sodium  carbonate 
was  saturated  in  solution  with  carbon  dioxide,  and  the 
resulting  bicarbonate  heated  in  a vacuum  at  300°  for  three 
hours. 

The  tungsten  trioxide  and  sodium  carbonate  were  com- 
bined in  a glass  bulb  as  per  figure.  A neutral  glass  is  de- 
sirable for  this  purpose,  and  the  bulb  should  be  made  of 
Jena  glass,  which  will  withstand  the  action  of  alkaline  car- 
bonates better  than  ordinary  glass.  If  sodium  carbonate 
dissolves  the  glass  no  error  will  be  introduced,  but  if  carbon 
dioxide  be  liberated  through  such  solution,  then  the  glass 
can  not  be  used.  To  determine  this  point  a blank  experi- 
ment was  made,  which  showed  that  the  total  weight  of  the 
bulb  and  sodium  carbonate  remained  unchanged,  while 
0.0017  grams  of  glass  were  dissolved;  hence  no  appreciable 
evolution  of  carbon  dioxide  occurred.  However  to  prevent 
any  possibility  of  such  loss,  a platinum  bulb  had  better  be 
used. 

It  was  found  that  moist  sodium  carbonate  could  be  heated 
to  a constant  weight,  by  heating  for  one  and  a half  hours, 
at  a temperature  of  300°  in  a vacuum;  and  in  this  bulb  the 
weight  after  standing  several  days  remained  unchanged. 


20 


To  insure  complete  desiccation  the  bulb  was  always  heated, 
double  the  required  length  of  time.  A water  pump  was 
used  to  produce  the  diminished  pressure  and  since  nothing 
can  be  perfectly  dried  in  a vacuum  resulting  from  such  a 
pump,  a calcium  chloride  tower  was  introduced.  But 
calcium  chloride  will  not  perfectly  desiccate  a gas,  so  that 
phosphorus  pentoxide  had  better  be  used.  However,  for 


the  preliminary  experiments  in  hand,  calcium  chloride  was 
sufficient. 

The  method  of  procedure  was  as  follows:  Some  sodium 

carbonate  was  introduced  in  the  bulb  and  heated  for  three 
hours  at  300°  in  a vacuum.  The  suction  was  disconnected, 
and  after  cooling,  the  combined  weight  of  bulb,  sodium 
carbonate,  and  dry  air  was  obtained.  Tungsten  trioxide 
was  then  introduced  through  a long  funnel,  the  bulb 
exhausted,  allowed  to  fill  with  dry  air  and  again  weighed. 
This  gave  the  weight  of  tungsten  trioxide.  The  weight  of 


21 


the  sodium  carbonate  further  than  being  present  in  excess 
need  not  be  known.  Water  was  added  and  the  bulb  heated 
in  a glass  air  bath,  so  that  the  course  of  the  reaction  could 
be  watched.  The  mixture  slowly  effervesced,  and  when 
the  action  had  ceased,  the  vacuum  apparatus  was  attached, 
and  the  water  distilled  off.  This  water  was  tested  and 
found  to  be  neutral.  The  calcium  chloride  tower  was  now 
introduced,  and  the  residue,  consisting  of  a mixture  of 
sodium  tungstate  and  carbonate,  was  heated  for  three  hours 
at  300°  in  a vacuum.  After  cooling  and  thus  allowing  the 
bulb  to  fill  with  dry  air,  it  was  detached  and  weighed. 
This  loss  in  weight  gave  the  carbon  dioxide  evolved.  It 
may  be  added  that  the  entire  bulb  should  be  inside  the  air 
bath,  until  the  water  has  been  removed;  and  then  the  upper 
portion  be  placed  outside  and  the  temperature  increased  to 
300°.  In  this  way  no  moisture  will  condense  in  the  head, 
and  the  stopper  remaining  perfectly  dry  will  not  become 
jammed.  The  stopper  should  not  be  lubricated. 

The  following  results  were  obtained,  from  impure 
material,  which  in  the  previous  experiments  in  this  paper 
gave  values  ranging  from  182.24  to  184.82,  and  which  was 
known  to  contain  iron,  manganese,  and  from  which  no 
effort  had  been  made  to  remove  molybdic  acid: 


Weight  of 

Weight  of 

Weight  of 

Na2C03 

W03 

co2 

Atomic  Weight 

grams 

grams 

grams 

of  Tungsten 

(O 

2.7 

2.0802 

0.3952 

183.60 

(2) 

2-3 

2.1937 

0.4173 

183.30 

(3) 

3-5 

4 0818 

0.7762 

183.38 

(4) 

3-8 

3.3629 

0.6394 

183.41 

These  numbers,  in  that  they  indicate  the  atomic  weight 
of  tungsten,  are  worthless;  in  that  they  show  promise  for 
th‘e  new  method,  are  of  value.  The  presence  of  impurity 
would  lower  the  result;  what  value  the  method  will  give 
for  pure  material  can  only  be  conjectured. 


22 


II.  THE  AMMONIUM  TUNGSTATES. 


The  ammonium  tungstates  are  divided  into  two  general 
classes,  the  “para salts”  and  the  “meta  salts”.  Laurent  first 
proposed  the  name  “paratungstates”;  and  to  these  salts  he 
gave  the  general  formula  5M20,  12WO3,  nH20.  <2)Marignac 
confirmed  this  formula  and  presented  numerous  other  types. 
Laurent  also  proposed  the  name  “metatungstates”  but 
they  were  first  prepared  by  (3)Margueritte.  Later  Scheibler 
and  Marignac  worked  on  them  and  arranged  them  under 
the  general  formula  M20,  4WO3,  nH20.  From  the  numer- 
ous formulas  proposed  for  the  type  members,  these  seem 
best  established,  and  the  salts  used  in  the  present  study 
conformed  to  them. 


Solubility  of  Ammonium  Paratungstate. 

(NH4)  10W12O41.  i iH20. 


The  solubility  of  the  “para  salt”  as  giver 
workers,  is  as  follows: 

1 by  different 

Investigator 

Ratio  of  Salt  to  Water 

Temperature 

Anthony 

1:25-28 

“Cold” 

Lot? 

1 :26.i 

10. 70 

< 4 

i:33-3 

“Cold” 

4 4 

1:5. 8-9.6 

IOO° 

Marignac 

1:22-38 

i5°-i8° 

Taylor 

i:59-3 

26° 

“ 

i :69-8 

21° 

* ‘ 

1:74. 

21° 

* ‘ 

1:52.7 

29° 

Solubility  of  Ammonium  Metatungstate 

Lotz 

1:0.84 

15° 

Riche 

1 :°-35 

“Ordinary” 

WAnn.  Chim.  Ph [3] , 21,  54.  (1847). 

WAnn.  Chim.  Pk.}  [3],  69 , 24.  (1863). 

(3 )Ann.  Chim.  Ph.}  [3],  17,  475.  (1846). 


23 


These  discrepancies  are  irritating.  The  present  material 
probably  did  not  contain  so  much  of  the  complex  salt  and 
was  consequently  less  soluble.  The  solubilities  of  pure 
ammonium  tungstates  need  to  be  determined  and  will  be  of 
value.  When  ammonia  is  passed  into  water  containing 
tungstic  acid,  a white  substance  remains  which  has  been 
called  “paratungstate”,  but  which  is  remarkably  insoluble. 
It  is  far  more  insoluble  than  any  ammonium  paratungstate, 
met  with  in  the  present  investigation. 


Ammonium  Paratungstate. 

(NH4)10  W12  041.  i iH20. 

When  a solution  of  “para  salt”  is  evaporated  at  slightly 
elevated  temperature,  monoclinic  needles  crystallize  out; 
when  evaporated  at  a boiling  temperature,  flat  plates  appear. 
These  needles  have  been  described  as  orthorhombic 
prisms  by  Kerndt,  Schabus  and  Marignac.  (^Examined 
microscopically  in  polarized  light  they  show  an  apparent 
parallel  extinction  and  give  a biaxial  interference  figure, 
with  the  acute  bisectrix  parallel  to  the  long  axis  of  the 
crystal;  and  therefore  appear  to  be  orthorhombic,  but  give 
these  orthorhombic  reactions  on  account  of  their  remarkable 
twinning  structure,  which  closely  resembles  the  wedge 
shaped  penetration  figures  seen  in  the  hydrated  Zeolites; 
more  particularly  Stiibite,  which  is  orthorhombic  in  form 
but  is  a complicated  monoclinic  twin.  It  is  an  interesting 
fact  that  these  ammoniated  and  hydrated  crystals  exhibit 
the  same  internal  structure  as  the  hydrated  Zeolites. 

Crops  of  crystals  usually  consist  of  mixtures  of  needles 
and  plates  in  varying  proportion;  and  many  previous 

b)I  am  glad  to  express  my  thanks  to  Professor  Amos  P. 
Brown,  under  whom  I have  had  the  pleasure  of  studying 
mineralogy,  and  who  has  rendered  most  valuable  assistance 
in  the  crystallographic  and  microscopic  study  in  this  paper. 


24 


analyses  have  undoubtedly  been  made  with  such  material. 
Such  a mixture,  consisting  largely  of  needles,  was  digested 
for  three  days  in  forty  times  its  weight  of  water.  The  water 
was  removed  and  the  same  amount  added  and  allowed  to 
stand  again  for  three  days.  The  needles  remaining  con- 
tained no  admixed  plates.  This  separation  does  not  prove 
that  the  plates  are  the  more  soluble,  for  they  are  smaller 
and  would  therefore  dissolve  out  first.  But  whatever  the 
reason  for  this  separation,  the  purpose  in  view  was 
accomplished;  the  needles  were  isolated.  These  on  analysis 
gave  the  following  data; 

Tungsten  trioxide,  determined  by  ignition  in  a porcelain 


crucible. 

“Para  needles”  W03  WOs 

grams  grams  per  cent. 

4.0016  3.4395  85.95 

3.1344  2.6938  85.94 

The  ammonia  was  determined  by  the  usual  distillation 
and  tritration  method. 

“Para  needles”  NH3  NH3 

grams  grams  per  cent. 

2.9265  0.15370  5.25 

2. £002  O.IO983  5.23 


The  water  was  determined  as  follows : The  salt  was  covered 
with  lead  oxide,  and  ignited  in  a combustion  tube  in  a 
current  of  dry  air;  the  water  and  ammonia  were  caught  in 
sulphuric  acid  and  weighed.  Subtracting  from  this  weight 
the  weight  of  the  ammonia,  the  weight  of  the  water  was 


obtained. 

“Para  needles”  NH3+H20  Water 

grams  grams  per  cent. 

1.2458  0.1813  9-31 

1.0636  0.1536  9.20 

1.5988  0.2262  8.91 


These  values  correspond  to  the  formula  (NH4)10  W12  041. 
1 iH20,  which  requires  W03)  85.87%;  NH3  5.24%;  H20 


25 


8.88% ; and  are  also  a confirmation  of  Marignac’s  formula. 

When  the  “para  needles”  are  crystallized  from  boiling 
water,  monoclinic  plates  separate  (Extinction  parallel  to 
diagonal  of  rhombic  section , axial  plane  lying  in  the  plane 
of  symmetry),  and.  to  obtain  these  with  no  admixed  needles, 
it  is  necessary  to  keep  the  water  at  the  boiling  point,  and  to 
remove  the  plates  from  the  boiling  solution  as  fast  as  they 
are  formed.  Some  plates  prepared  in  this  way,  gave  on 
ignition  the  following  per  cent,  of  tungsten  trioxide. 


‘ Tara  plates’  ’ 

wo. 

wo, 

grams 

grams 

per  cent. 

0.6931 

0.6170 

89.02 

0.2528 

0.2249 

88.96 

0.3216 

0 2860 

88.93 

05905 

0-5253 

88.96 

The  theoretical  requirement  of  tungsten  trioxide  for 
(NH4)10  W12  041.  5H20,  is  88.83%  an<3-  this  also  confirms 
Marignac’s  formula.  A comparison  of  these  two  para  salts 
is  as  follows: 

“Para  needles.”  (NH4)10  W12  041.  iiH20. 

‘ Tara  plates.’  ’ (NH4X0  Wu  041-  5H20. 

Thus  it  would  appear  that  the  “para  needles”  in  boiling 
water,  lose  six  molecules  of  water. 

Ammonium  Metatungstate* 

(MH4)2  W4  018.  8H20. 

TMargueritte  first  prepared  this  salt  by  boiling  the  para 
salts  with  tungstic  acid.  f?)  Laurent  prepared  it,  by  the 
continued  boiling  of  the  aqueous  solution  of  the  para  salts. 
While  (3)Scheibler  made  it  by  heating  the  para  salt  to  250°, 
until  ammonia  was  given  off,  causing  a partial  separation 

OAnn.  Chim.  Fh.}  [3],  X 7*475-  (1846). 

WAnn.  Chim.  Fh .,  [3],  2if  62  (1847). 

(3 )J.  prakt.  83*304,  (1861). 


26 


of  tungstic  acid,  then  dissolving  the  residue  in  water  and 
allowing  to  crystallize.  This  method  was  adopted  by 
(l)Persoz  and  later  by  ^Marignac. 

Scheibler  describes  the  salt  as  crystallizing  in  large  tetra- 
gonal octahedra,  which  effloresce  in  the  air.  If  the 
crystals  have  been  scratched  or  bruised,  they  quickly  lose 
water  and  become  opaque.  Marignac  observed  that  the 
crystals  lose  seven  molecules  of  water  at  ioo°,  and  the 
remaining  molecule,  is  not  driven  out  below  200°.  Riche 
noticed  the  same  behavior.  When  alcohol  is  added  to  a hot 
solution  of  the  “meta  salt”,  the  salt  (NH4)2  W4  013.  6H20 
separates,  and  according  to  Marignac,  loses  five  molecules 
of  water  at  ioo°. 

In  the  present  investigation  the  “meta  salt”  was  prepared 
by  boiling  an  aqueous  solution  of  the  “para  salt”  for  two 
or  three  da}7s,  evaporating  to  small  bulk  and  allowing  the 
sirupy  liquid  thus  obtained  to  stand.  Large  transparent 
tetragonal  octahedra,  were  obtained.  After  three  or  four 
recrystalizations,  the  crystals  became  almost  colorless,  but 
the  yellow  tint  was  difficult  to  remove.  Boiled  with  purified 
bone  black  the  greater  part  of  the  original  brown  color  may 
be  removed.  The  crystals  have  a high  index  of  refraction, 
as  also  the  solution.  These  crystals  of  “meta  salt”  were 
also  prepared  by  heating  the  “para  needles”  at  150°,  for 
four  hours. 

On  analysis  the  salt  gave  3.05  per  cent,  of  ammonia. 
“Meta  Salt”  NH3  NH3 

grams  grams  Per  cent. 

0.5016  0.01531  3.05 

This  corresponds  to  (NH4)2  W4013.  8H20,  which  contains 
3.02%  of  ammonia,  confirming  Scheibler’s  formula.  The 
characteristic  physical  properties  were  in  such  accord  with 
the  published  data,  that  further  analysis  was  not  undertaken. 


WAnn.  Chrm.  Ph .,  [4],  ftioi.  (1864). 
WAnn.  Chim.  Ph. , [4],  3,  72.  (1864). 


27 


Colloidal  Ammonium  Tung-state. 

(NH4)2  W6  019.  4 or  6 H20. 

On  repeating  the  method  of  Scheibler  to  obtain  the  “meta 
salt”  (i.  e.  heating  the  “para  needles”  to  250°),  a colloidal 
“gum”  was  obtained.  As  many  as  twenty  experiments 
failed  to  substantiate  his  claims,  however,  at  150°  the 
“meta  salt”  was  produced.  This  “gum”  would  dry  hard 
and  transparent,  and  had  a high  index  of  refraction.  It  did 
not  cement  itself  to  porcelain,  in  the  way  “colloidal  tung- 
stic acid”  is  said  to,  but  would  shrink  away  from  the  sides 
of  the  containing  vessel,  and  could  easily  be  removed. 
Under  the  microscope  “para  needles”  were  found  imbedded 
in  it,  and  these  could  be  removed  by  dialysis.  The  fraction 
passing  through  the  parchment  paper  in  a few  hours, 
would  crystallize  in  tetragonal  octahedra;  later  fractions 
in  “para  needles”,  and  still  later  fractions  would  not 
crystallize  at  all  but  consisted  largely  of  “gum”  which 
had  passed  through.  This  “gum”  therefore  when  first 
prepared,  consists  of  a mixture  of  “para  salt”,  “meta 
salt”,  and  a “colloidal  salt.” 

The  best  condition  for  getting  a large  yield  of  the 
“gum”  is  as  follows:  Pulverized  “para  needles”  are 

spread  out  on  a watch  glass,  and  heated  in  an  air  bath  at 
220°  for  one  hour.  The  air  bath  must  allow  the  escape  of 
water  and  ammonia.  The  product  is  covered  with  water 
and  boiled  vigorously  for  fifteen  or  twenty  minutes,  when 
a clear  (but  darkened)  heavy  liquid  results.  This  is  filtered 
away  from  any  residue  and  on  evaporation  dries  into  the 
“gum”  with  an  almost  quantitative  yield.  On  standing 
several  days  in  water,  the  residue  will  pass  into  the  “gum” 
without  previous  boiling.  At  higher  temperatures  consid- 
erable tungstic  acid  is  separated  and  the  yield  not  so  good. 
The  “meta”  salt  free  from  “para”  must  be  heated  to  250°, 
before  yielding  the  “gum”,  and  the  yields  are  nothing  like 
so  large,  as  by  starting  with  the  “para  salts.” 


28 


A marked  darkening  of  the  original  white  salt  is  noticed 
after  heating.  Different  fractions  of  the  “para  salts”  yield 
the  “gum”  with  different  degrees  of  readiness.  These 
facts  point  to  the  presence  of  some  impurity  which  may 
affect  the  transformations. 

After  dialyzing  a portion  of  the  “gum”  for  six  days  it 


gave  the  following 

analysis: 

“Gum” 

wo. 

WO, 

grams 

grams 

Per  cent. 

0.61 50 

0-5447 

88.57 

“Gum” 

nh3 

nh3 

grams 

grams 

Per  cent. 

0.4825 

0.01279 

2.65 

1.3776 

0.03848 

2.79 

Another  sample  was  dialyzed  for  thirteen  days,  through 
parchment  paper,  using  ten  changes  of  water  of  two  and 
one-half  liters  each.  The  dialyzer  had  a diameter  of  fifteen 
centimeters.  After  four  or  five  days,  the  increase  of  volume 
in  the  inner  vessel  ceased.  The  resulting  colloidal  salt, 
when  dried  on  the  water  bath  and  allowed  to  stand  in  the 
air,  slowly  increased  in  weight.  But  when  dried  at  the 
ordinary  temperature  and  allowed  to  stand,  it  decreased  in 
weight.  A portion  of  the  “colloidal  salt”  dried  on  the 
water  bath,  gave  the  following  analysis: 


“Colloidal  Salt” 

wo3 

W03 

grams 

grams 

Per  cent. 

0.4469 

0.4089 

91.49 

0.4523 

0.4143 

91.60 

“Colloidal  Salt” 

NH, 

nh3 

grams 

grams 

Per  cent. 

0-6334 

0. 01520 

2.40 

0.5985 

0.01415 

2.36 

These  results  point  to  the  formula  (NH4)2 

, w.  019.  4H2Ot 

which  requires 

ammonia  2.24%  and  tungsten  trioxide 

91.82%. 


29 


In  the  same  way  another  portion  of  “gum”  was  dialyzed 
for  fourteen  days,  using  nearly  double  the  amount  of  water 
previously  used.  (Twelve  changes  of  water  of  three  and  a 
half  liters  each).  The  resulting  “colloidal  salt”  dried  at 
the  ordinary  temperature  gave  the  following  analysis: 


“Colloidal  Salt” 

W03 

WO, 

grams 

grams 

Per  cent. 

0.1227 

O.IIOI 

89-73 

0.2100 

0.1885 

89.76 

“Colloidal  Salt” 

nh3 

NHS 

grams 

grams 

Per  cent. 

0.9243 

0.01996 

2.16 

1. 0301 

0.02184 

2.12 

These  percentages  are  close  to  the  formula  (NH4)2  W6 
019.  6H20,  which  requires  ammonia  2.29%,  and  tungsten 
trioxide  89.69%.  This  sample  was  dried  at  the  ordinary 
temperature,  the  previous  one  at  ioo°.  Since  the  salt  loses 
weight  on  standing,  it  is  likely  that  the  additional  water  is 
not  such  a definite  number  of  molecules  as  these  analyses 
would  indicate. 

To  compare  the  percentage  of  ammonia,  in  the  different 


salts,  the  following  table  is  given: 

Salt  NH3  Per  cent. 

“Para  needles”  5.24 

“Para  plates”  5.42 

“Meta  salt”  3.02 

“Colloidal  Salt”,  (dialyzed  6 days)  2.72 

“ “ ( “ 13  “ ) 2-38 

“ “ ( “ 14  *•  > 2.14 


The  dialyzed  salt  dries  hard  and  clear  like  glass,  with  a 
yellowish  tint,  contains  no  embedded  crystals,  and  under 
no  conditions  could  it  be  made  to  crystallize.  It  has  a high 
index  of  refraction  and  is  mixable  with  water  in  nearly  all 
proportions.  It  may  prove  of  value  as  a mounting  medium 
in  microscopic  work,  and  also  for  the  mechanical  separation 
of  minerals. 


30 


The  solution  has  an  acid  reaction  and  absorbs  ammonia 
with  avidity.  One  long1  series  of  dialyzation  was  spoiled, 
by  working  with  ammonia  in  the  same  room,  the  “colloidal 
salt”  changing  to  the  “meta”  and  “para”  salts.  By  treat- 
ing the  solution  of  the  “colloidal  salt”  with  tenth-normal 
ammonia,  till  the  acidity  is  barely  neutralized,  it  passes 
into  the  “meta  salt”.  Unless  care  is  used  considerable 
amounts  of  the  “para  salts”  will  be  formed. 

Under  certain  conditions  the  “colloidal  salt”  passes  into 
a white  modification,  which  on  microscopical  examination 
proved  to  be  an  emulsion,  the  globules  closely  resembling 
fat  globules.  On  drying  the  white  emulsion  would  gradu- 
ally pass  into  the  transparent  variety.  The  emulsion  can 
be  produced  by  cooling  a clear  concentrated  solution,  with 
ice  water.  Oftentimes  a more  dilute  solution,  would  be 
filled  with  spurious  clouds,  floating  in  suspension,  and 
which  appeared  to  be  some  foreign  matter.  This  could  not 
be  filtered  out  and  was  a source  of  annoyance,  until  it  was 
examined  microscopically,  and  found  to  be  the  emulsion. 
Emulsions  are  common  enough  among  organic  substances, 
but  are  rarely  observed  with  inorganic  salts. 

At  first  it  was  thought  that  this  “colloidal  salt”  might 
be  “colloidal  tungstic  acid”,  but  since  after  prolonged 
dialysis,  the  ammonia  could  not  be  removed,  it  appears  to 
be  a colloidal  ammonium  tungstate. 

The  history  of  ‘ colloidal  tungstic  acid”  is  of  some 
interest.  (^Graham  in  1864,  reported  the  existence  of 
“colloidal  tungstic  acid”,  which  he  prepared  by  treating  a 
five  per  cent,  sodium  para  tungstate  solution  with  dilute 
hydrochloric  acid  and  dialyzing  the  mixture.  The  result- 
ing heavy  liquid  had  a specific  gravity,  such  that  glass 
would  float  on  it.  (2)Sabanejeff  made  a molecular  weight 


WProc.  Roy.  Sue London , $3,340.  (1864). 

Russian  Ch.  Soc .,  2$ti.  (1889). 


3i 


determination  using  cryoscopic  methods,  and  reported  the 
structure  3WO,.  H20.  (d^ater  he  retracted  his  determina- 
tions, and  published  an  article  on  the  ‘‘Non-existence  of 
colloidal  tungstic  acid,”  saying  that  he  had  previously 
taken  Graham’s  word  for  the  composition  of  the  “gum”. 
On  examination  he  found  it  was  impossible  to  dialyze  out 
the  sodium,  and  concluded  that  it  was  amorphorus  sodium 
metatungstate.  His  proof  of  this  is  open  to  criticism,  for; 
he  states  that  the  salt  had  a marked  acid  reaction;  his 
analyses  do  not  conform  closely  to  the  theoretical  for 
sodium  metatungstate;  and  the  periods  of  dialysis  used 
were  not  long  enough  to  thoroughly  separate  the  material: 
The  conversion  of  one  form  into  the  other  was  rather 
violent.  Sabanejeff  changed  the  amorphous  salt  into  the 
crystallized  variety,  by  heating  to  i30°-i50°,  in  a sealed 
tube  with  an  excess  of  water.  This  temperature  is  about 
the  same  as  that  which  changes  the  ammonium  “para  salt” 
to  the  “meta  salt”  and  seems  altogether  too  high  to  prove 
the  dimorphism,  of  the  two  sodium  salts.  Had  the  acidity 
of  his  colloidal  salt  been  gradually  neutralized  with  sodium 
bicarbonate  or  carbonate,  the  salt  might  have  reverted  to 
the  crystallized  form,  and  its  dimorphism  thus  disproved. 
It  seems  probable  that  his  dimorphous  colloidal  sodium 
metatungstate  may  prove  to  be  a colloidal  sodium  tung- 
state analogous  to  , the  colloidal  ammonium  tungstate  pre- 
pared in  the  present  investigation. 


Temperature  at  which  the  Ammonium  Salts  begin  to  lose 
Ammonia* 

Some  “para  needles  were  placed  in  a glass  U- tube  im- 
mersed in  an  oil  bath;  dry  air  rapidly  passed  over  them  and 
into  Nessler’s  solution.  It  was  found  that  if  the  glass  tube 


WZtschr,  anorg.  Ch.  14,354-  (1897). 


32 


leading  into  the  solution,  was  etched  on  the  inner  surface, 
a brown  ring  would  form  on  the  roughened  surface,  several 
minutes  before  the  solution  showed  any  traces  of  color. 
The  moment  of  formation  of  this  brown  ring,  was  taken  as 
the  signal  for  the  first  appearance  of  ammonia,  and  the 
temperature  of  the  bath  noted.  In  this  manner  the  “para 
needles”  began  to  lose  ammonia  at  6o°.  The  “para  plates” 
at  the  same  temperature,  and  the  “meta  salt”  at  120°. 

It  is  significant  that  the  “meta  salt”  should  begin  to  lose 
ammonia  at  120°;  it  was  prepared  at  150°.  It  seems  im- 
probable that  a salt  which  begins  to  lose  ammonia  at  120° 
could  be  prepared  at  250°,  as  recorded  by  Scheibler. 

Marignac  and  others  dry  the  “para  salts”  at  ioo°  and 
attribute  the  loss  to  expulsion  of  water,  but  a part  of  that 
loss  is  ammonia.  However,  the  ammonia  that  escapes 
below  ioo°  is  but  a trace. 


Action  of  Dry  Ammonia  Gas  on  “Para  Needles ”♦ 

The  effect  of  ammonia  on  “para  needles”  was  determined 
as  follows:  A boat  of  needles  was  placed  in  a bent  tube  im- 
mersed in  paraffin.  Ammonia  gas  (dried  by  lime  and 
caustic  potash)  was  passed  over  it,  and  escaped  through  0.75 
cm.  mercury  and  9.00  cm.  of  water,  so  that  the  gas  was  under 
a pressure  of  about  fourteen  millimeters  of  mercury,  in  excess 
of  the  atmospheric  pressure.  After  heating  for  one  and  a half 
hours  the  boat  was  placed  in  a capsule  and  weighed.  The 
percentage  of  ammonia  was  then  determined.  The  loss  in 
weight,  together  with  the  percentage  of  ammonia  furnish 
data,  from  which  the  changes  in  the  salt  may  be  calculated. 


Action  of  Dry  Ammonia  Gas  on  Ammonium  Paratungstate* 


33 


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v o S 


10  N 00  oo  ts  to  10 

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34 


Attention  is  directed  to  the  nearly  constant  loss  of  water ; and 
that  at  130°  the  maximum  amount  of  ammonia  is  absorbed.  At 
250°  tungsten  trioxide  was  separated. 

These  ammonio-addition  salts  are  quite  unstable;  when 
dissolved  in  water,  the  water  is  made  alkaline  and  ‘ ‘para 
needles”  crystallize  out;  when  allowed  to  stand  in  the  air 
they  revert  to  their  original  weight,  and  percentage  of  ammo- 
nia, as  evidenced  in  the  following  experiments:  Two  boats 

of  “para  needles”  placed  side  by  side  in  the  same  U-tube 
were  heated  together  in  dry  ammonia  gas  at  130°  for  one 
and  a half  hours.  The  ammonia  in  one  was  determined  at 
once;  the  companion  boat  was  allowed  to  stand  over  night, 
before  determining  the  ammonia. 


“Para  needles” 

NHS 

NH, 

grams 

grams 

Per  cent. 

Boat  A.  0.8754 

0.06242 

7-i3 

Companion  Boat  A.  0.9718 

0.05034 

5.18 

Boat  B.  0.8744 

0.05859 

6.70 

Companion  Boat  B.  0.9321 

0.04866 

5.22 

Companion  Boat  B,  after  standing  over  night,  weighed 
0.9319  grams.  It  appears  therefore  that  the  salt  has  lost 
its  added  ammonia,  and  absorbed  its  lost  water. 


Action  of  Moist  Ammonia  Gas  on  the  “Meta  Salt”  at  the 
Ordinary  Temperature. 

A boat  containing  0.9874  grams  of  ;‘meta  salt”  was 
placed  in  a vacuum  desiccator,  over  ammonium  hydroxide. 
After  standing  several  hours  the  transparent  crystals  were 
found  to  be  replaced,  by  a white  salt  covered  with  water. 
This  water  was  removed  by  spontaneous  evaporation  in  the 
air,  and  the  residue  weighed  0.9327  grams  and  contained 
0.04803  grams  ammonia,  equivalent  to  515%,  or  3.83  mole- 
cules of  ammonia  added.  Hence  the  “meta  salt”  has  been 


35 


changed  by  moist  ammonia  gas,  at  the  ordinary  tempera- 
ture into  the  “para  needles”,  and  the  conversion  has  been 
practically  quantitative. 

The  “para  needles”  being  a hundred  times  more  insol- 
uble than  the  “meta  salt”,  have  crystallized  out  from  the 
water  of  crystallization  of  the  latter.  In  other  words  the 
water  of  the  old  salt  has  been  pushed  out  by  the  new  salt, 
and  the  new  salt  is  found  “swimming”  in  the  water  of 
crystallization  of  the  old  salt.  On  several  days  standing 
the  amount  of  water  in  the  boat  gradually  increased,  so  that 
water  evidently  slowly  distills  into  the  boat. 


Action  of  Moist  Ammonia  Gas  on  the  “Meta  Salt”  at  J00°* 

“Meta  salt”  treated  with  ammonia  passes  to  the  “para 
needles,”  and  a solution  of  these  at  ioo°  changes  to  the 
“para  plates”;  so  that  the  action  of  moist  ammonia  on  the 
“meta  salt”  at  ioo°  can  almost  be  predicted.  A boat  con- 
taining 0.4408  grams  “meta  salt”  (placed  in  the  same 
apparatus  used  for  determining  the  action  of  dry  ammonia 
on  the  “para  needles”),  was  treated  with  moist  ammonia 
gas  at  ioo°,  for  one  hour.  After  treatment  the  salt  weighed 
0.4189  grams;  after  standing  sixty  hours  in  the  air  it 
weighed  0.4186  grams.  This  contained  0.02276  grams  of 
ammonia  equivalent  to  5.44%,  or  4.04  molecules  of  added 
ammonia.  Hence  at  ioo°  moist  ammonia  gas  transforms 
the  “meta  salt”  into  the  “para  plates.”  Dry  ammonia 
gas  would  probably  form  the  ammonio-addition  product 
produced  at  that  temperature. 


36 

THEORETICAL  CONSIDERATIONS. 


Normal  Ammonium  Tungstate* 

The  normal  sulpho-salt  (NH)2WS4  exists  and  one  might 
expect  the  existence  of  the  corresponding  oxygen  salt. 
However,  normal  ammonium  tungstate  has  never  been 
prepared.  (^Marignac  by  the  spontaneous  evaporation  of  a 
solution  of  ‘ ‘para  salt’  ’ , in  a bell  jar  over  lime  (which  would 
absorb  water  and  not  ammonia) , obtained  a salt  of  the  com- 
position 2(NH4)20.  3WO3.  3H20.  This  salt  was  soluble 
in  cold  water  but  soon  changed  to  the  “para  salt.”  In  the 
air  it  gave  off  ammonia  reverting  to  the  “para  salt.” 

Various  methods  have  been  suggested  in  the  present 
work,  to  make  the  normal  salt.  Among  which  may  be 
mentioned  the  following: 

1.  Pass  ammonia  into  a solution  of  the  “meta  salt” 
cooled  to  zero  degrees. 

2.  Pass  ammonia  into  the  “colloidal  salt”  cooled  to  zero 
degrees. 

3.  Pass  ammonia  into  benzene  (or  some  other  liquid  not 
mixable  with  water)  in  which  is  suspended  the  ammonium 
salt. 

4.  Action  of  liquid  ammonia  on  tungstic  acid. 

Of  these  methods  the  first  only  was  tried,  a crystallized 
Salt  obtained  which  in  the  air  lost  ammonia,  but  it  was  not 
analyzed. 

The  ratio  between  the  ammonia  and  tungsten  trioxide, 
in  the  different  salts  is  tabulated  as  follows: 


Salt 

NH, 

wos 

Theoretical  Normal  Salt 

1.0 

0.5 

Marignac’s  Salt  (unstable) 
“Meta  Salt’’ 

1.0 

o.75 

1.0 

2.0 

“Para  Salt” 

1.0 

1.2 

WAnn.  Chim.  Ph. , [3],  69,22.  (1863). 


37 


From  these  ratios  it  is  seen  that  Marignac’s  salt  is  the 
closest  to  the  normal  ratio  that  has  yet  been  prepared,  but 
it  was  not  stable  at  the  ordinary  temperature.  Of  the  other 
salts,  the  “para  salt”  is  the  closest  to  the  normal  ratio. 
The  para  ammonio-addition  salts  prepared  in  this  investi- 
gation are  unstable,  easily  losing  their  excess  of  ammonia. 
It  seems  therefore  that  at  the  ordinary  temperature, 
tungsten  can  not  hold  any  more  ammonia  than  that  ex- 
pressed by  the  para  ratio.  It  is  believed  that  the  formation 
and  preservation  of  the  normal  salt  is  simply  a question  of 
temperature. 

Water  of  Crystallization* 

In  boiling  water  the  “para  needles”  lose  exactly  six 
molecules  of  water  and  crystallize  out  as  “para  plates.” 
Five  molecules  of  water  remain  in  the  salt,  and  it  is  sig- 
nificant that  five  ammonium  oxide  molecules  remain  also. 
Possibly  five  ammonium  oxide  influence  five  water  in  such 
a manner,  that  these  molecules  are  more  firmly  bound  or 
linked  than  the  others.  Whatever  explanation  may  be 
advanced,  the  fact  remains  that  six  molecules  of  water  are 
driven  out  at  ioo°,  and  five  are  not. 

The  “meta  salt”,  (NH4)2W4013.  8H20,  at  ioo°  loses 
seven  molecules  of  water.  The  remaining  molecule  can 
not  be  driven  out,  below  200°.  “The  “meta  salt”  from 
alcohol  (NH4)2  W4  013.  6H20,  at  ioo°  loses  five  molecules 
of  water,  and  the  remaining  molecule  behaves  as  before. 
In  these  salts  one  molecule  of  water  must  be  very  differently 
combined  from  the  others,  for  one  requires  200°  of  temper- 
ature to  remove  it,  while  the  others  leave  the  salt  quite 
rapidly  even  at  the  ordinary  temperature.  The  number  of 
water  molecules  remaining,  again  correspond  to  the  num- 
ber of  ammonium  oxide  molecules,  and  the  probability 
increased  that  one  ammonium  oxide  influences  one  hydro- 
gen oxide. 


38 


These  two  salts  may  be  written: 

[2  NH4  OH.  4 W03]  . [7  H.O] 

[2  NH4  OH.  4 W03]  . [5  H20] 

At  ioo°  in  the  air  the  water  is  split  off  from  both  salts, 
and  the  common  residue  or  nucleus  [2  NH4  OH.  4 WOs] 
remains,  which  is  stable  up  to  200°. 


Ammonia  Content* 

The  para  “needles”  and  “plates”  begin  to  lose  ammonia 
at  6o°;  the  “meta  salt”  at  120°.  If  the  ammonia  in  these 
salts  is  combined  in  the  same  manner,  it  ought  to  be  given 
off  at  the  same  temperature.  Such  is  not  the  case,  and 
consequently  it  looks  as  though  part  of  the  ammonia  was 
differently  combined  or  linked  than  the  rest.  At  150°  the 
“para  salts”  lose  four  molecules  of  ammonia,  and  revert  to 
the  “meta  salt.”  The  “meta  salt”  on  the  addition 
of  four  molecules  of  ammonia  advances  to  the  “para 
salt”.  The  commonest  double  salt  of  sodium  with 
ammonium  paratungstate,  has  the  composition  Na4 
(NH4)6  W12  041.  i5H20  (Knorre,  Marignac,  Hallopeau.) 
Four  molecules  of  ammonia  have  been  replaced  by  four 
molecules  of  sodium.  The  fact  that  all  the  ammonia  has 
not  been  displaced  by  sodium,  indicates  that  four  molecules 
are  differently  combined  than  the  others,  and  probably 
these  are  the  same  four  which  are  lost  at  150°,  (or  on  long 
standing  in  water,  even  at  the  ordinary  temperature.) 


T ransf  ormations* 

The  transformations  in  this  series  of  salts,  are  of  interest. 
The  entire  series  may  be  prepared  from  the  first  member,  or 
the  entire  series  may  be  prepared  from  the  last  member.  In 
fact,  the  whole  series  may  be  prepared  from  any  member. 


39 


Temperature 

of  formation.  Series 

(Below  ioo°)  “Para  needles”  (NH4)10W12O41.  iiH20 

(ioo°)  “Para  plates”  (NH4)10W12O41.  5H20 

(150°)  “Meta  salt”  (NH4)2  W4  013.  8H20 

(220°)  “Colloidal  salt”  (NH4)2  W6019.  4or6H20 

Before  taking  up  the  transformations,  attention  is  called 
to  the  difference  between  the  last  two  salts.  This  differ- 
ence is  2WO3.  2 or  4H20.  (i) Gibbs  in  his  classic  work,  on 

the  complex  inorganic  acids,  pointed  out  the  existence  of  a 
“homologous  series”  of  metatungstates  having  a com- 
mon difference  2W03.  RO.  The  difference  noticed  here, 
while  not  exactly  the  common  difference  discovered  by  him, 
is  equivalent  to  it,  as  far  as  the  tungsten  trioxide  is  con- 
cerned. 

The  two  “para  salts”  (in  the  series)  on  long  standing  in 
solution,  at  the  ordinary  temperature  revert  to  the  “meta 
salt”.  The  “colloidal  salt”  on  absorbing  ammonia,  reverts 
to  the  “meta  salt”.  The  “meta  salt”  on  standing  reverts 
to  the  residue  [2NH4  OH.  4WOj . This  residue,  therefore 
may  be  considered  a decomposition  product  or  nucleus  of 
the  whole  series.  It  is  the  most  stable  portion  in  the  entire 
series;  when  it  is  attacked,  the  structure  of  the  salt  is 
broken  down,  and  tungstic  acid  separated.  It  is  well  known 
that  the  “meta  salts”  are  broken  down  by  acids  or  alkalies 
only  with  difficulty. 

Beginning  with  the  first  member,  we  may  go  down  the 
series,  by  physical  means:  “Para  needles”  heated  to  ioo° 

(in  water)  go  the  “para  plates”.  The  “plates”  at  150° 
(in  air)  pass  into  the  “meta  salt”.  The  latter  heated  to 
250°  changes  to  the  “colloidal  salt.” 

Again,  we  may  proceed  down  the  series  by  chemical 
means.  “Para  needles”  treated  with  acetic  acid  go  to 


WProc.  Am.  As.  Adv.  Sci .,  47,i,  (1898)  and  previous  papers. 


40 


the  (^“para  plates”.  The  “para  plates”  boiled  with  tung- 
stic acid  or  dilute  mineral  acids  pass  into  the  “meta  salt”. 
The  “meta  salt”  as  yet  has  not  been  changed  into  the  “col- 
loidal salt”  by  chemical  means;  boiling  with  tungstic  acid 
did  not  produce  it. 

To  reverse  the  transformations:  Beginning  with  the  last 

member  we  may  proceed  up  the  series,  by  chemical  means. 
The  acidity  of  the  “colloidal  salt”  neutralized  with  ammo- 
nia, produces  the  “meta  salt”.  The  “meta  salt”  on  the 
addition  of  four  molecules  of  ammonia  at  ioo°,  advances  to 
the  ' ‘para  plates”.  The  “para  plates”  on  the  addition  of  water 
at  the  ordinary  temperature  proceed  to  the  “para  needles”. 

From  these  considerations  it  appears  probable,  that  a 
common  nucleus  runs  through  the  whole  series,  and  that 
the  nucleus  is  [2NH4OH.  4WO3].  The  molecular 
weight  of  this  nucleus  is,  as  yet  unknown,  it  may 
be  a polymer,  or  it  may  be  one-half,  which  would  cor- 
respond to  Gibbs’  difference  [RO.  2WO3],  and  might  be 


[NH4  OH.  2WO3],  and  until  molecular  weight  determina- 
tions have  been  made  the  salts  may  be  written  with  this 
in  mind. 


b) Gibbs  Am.  Cli.  «/.,  ^229.  (1879). 

Gibbs  states  that  the  salt  formed  with  acetic  acid  has  the 
composition  (NHJ10  W12  041.  6H.20,  and  adds  that  it  appears 
to  be  the  same  salt,  to  which  Marignac  attributed  5H20. 
The  temperature  of  crystallization  may  clear  up  the  dis- 
crepancy. 


r 1ST  FT 

written 


>0.  2WO3] 


The  simplest  view  of  the  mat- 
ter would  favor  the  nucleus 


PARA  AMMONIO-SUBSTITUTION  SAET. 


41 


> 
3 B 


O 


> 

& 

> 


O 

3 


4^ 

1 — 1 1 — 1 1 — 1 1 — 1 1 — 1 1 — 1 1 — 1 1 — 1 1 — 1 

aawwwaniffitri 
o o o o o o o o o 
a w w w tn  a a k w 

K)K)W(OK)MWMn 

0000000. 00 


o k a k w k a w a 
^ o o b o b b o b 
mw.w.s  w w a w 


o 

tz5 

HH 

O 

> 

o 

o 


o 

3 

►d 

& 

o 

u 

Cl 

o 

Xfi 


n g ^ ^ 


►d  2 


to  to  o\  a 

I 1 I 1 l 1 I 1 

3 3 SZJ  3 

3 3 3 3 
o o o o 
3 3 w 3 

to  to  to  to 

3 3 3 3 
o o p o 


10  M 4* 

I I 1 I 1 I 1 

^ 3 3 Szj 
O o W W 

^^bb 


w w 


0 

1  1 

3 

o 


4^  to  Cn  (J\  0\  tn  Ln  -t± 

1 — 1 1 — 1 1 — 1 1 — 1 1 — i 1 — 1 1 — 1 1 — 1 1 — 1 

333333333 


E 

o 


3 

o 


AMMONIUM,  “PARA”  AND  “META”  TUNGSTATES. 


42 


These  tables  suggest  the  presence  of  “nuclei”  and  “side- 
chains”.  The  “para  salts”  appear  to  be  polymers  of  the 
“meta  salts”,  linked  together  by,  or  to  which  are  added, 
the  “side-chains”.  The  “side-chains”  may  be  split  off  by 
physical  or  chemical  means,  and  substitutions  appear  to 
take  place  in  them.  Where  transformations  require  the 
splitting  off  of  part  of  the  structure,  both  physical  and 
chemical  means  may  be  employed  to  accomplish  the  desired 
end.  But  where  transformations  demand  the  addition  of 
these  parts,  then  chemical  means  only  can  accomplish  the 
purpose. 

(^Smith  and  Hardin  have  demonstrated  the  tendency  of 
tungsten  trioxide  itself,  to  polymerize.  And  after  such 
polymerization  the  material  is  insoluble  in  sulphur  mono- 
chloride, whereas  before,  it  is  soluble.  The  polymer- 
ized ammonium  salts  in  this  series,  are  over  a hundred 
times  more  insoluble  than  the  unpolymerized. 

It  is  significant,  that  the  temperature  which  breaks  down 
the  “para  salt”  into  the  “meta  salt”  (i.  e.  150°),  is  not  far 
from  that  temperature  (130°),  at  which  the  “para  salt”  in 
ammonia  gas,  is  able  to  take  on  the  maximum  amount  of 
ammonia.  In  other  words,  the  polymer  absorbs  the  most 
ammonia  at  a temperature  near  its  rupture  temperature. 
It  looks  as  though  the  polymer  when  “opened  up”  was 
enabled  to  “take  in”  more  ammonia. 

There  is  no  reason  why  the  compounds  of  carbon,  should 
have  a monopoly  over,  “homologous  series”,  “polymer- 
izations” “ring  formations’  ’,  “side-chains”,  “substitution 
products”  or  “gums”. 

Organic  “gums”  are  supposed  to  be  high  polymers  of 
some  simple  form,  and  the  polymerization  is  usually  accom- 
panied with  insolubility  and  non-crystalline  character.  The 
“gum”  in  the  present  investigation  appears  to  be  an  ammo- 


WJ.  Am.  Ch.  &oc. , 21,1007.  (1899). 


43 


nium  salt,  but  no  surprise  will  be  expressed,  if  it  proves  to 
be  an  acid  salt  of  ‘ ‘colloidal  tungstic  acid’  ’ and  ammonium 
metatungstate.  If  “colloidal  tungstic  acid”  exists,  it 
would  probably  be  a polymer  of  tungsten  trioxide,  and  its 
affinity  for  ammonia  would  be  so  great  that  only  with 
difficulty  could  the  two  be  separated.  In  one  experiment, 
a long  process  of  dialyzation  was  ruined  by  the  presence  of 
ammonia  in  the  atmosphere  of  the  room;  and  who 
knows  how  much  ammonia  the  other  experiments  absorbed. 
Traces  of  ammonia  would  neutralize  the  work  performed 
by  days  of  dialyzation.  The  subject  needs  to  be  further 
investigated. 

It  is  hoped  that  benzylamine  tungstate  will  form  a similar 
series  of  salts,  and  yielding  more  readily  to  organic 
methods,  facts  concerning  their  molecular  magnitude  and 
constitution  may  be  developed. 


•S: 


